System for controlling temperature of subsea equipment

ABSTRACT

An underwater assembly includes a flow control device and an actuator coupled to the flow control device, where the actuator is configured to actuate the flow control device. The underwater assembly further includes an insulated housing surrounding the flow control device and the actuator, where the insulated housing is configured to retain heat. The underwater assembly also includes a thermal control system comprising a heat exchanger configured to control a temperature of the actuator.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

A variety of subsea equipment, such as mineral extraction equipment, maybe subjected to high temperatures and low temperatures. For example,mineral extraction equipment, such as valves, actuators, and other flowcontrol mechanisms, may experience elevated temperatures as fluids flowthrough the equipment. In addition, the sea water is often very cold atlocations of the mineral extraction equipment, thereby subjecting theequipment to cold temperatures in addition to the elevated temperatures.Unfortunately, hot and cold extremes may subject the equipment tothermal stress, damage, or failure. For example, certain electronicsand/or actuators may eventually fail at extreme temperatures or as aresult of thermal cycles. Accordingly, a need exists to maintaintemperature within an acceptable range to reduce the possibility ofdamage or failure.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features, aspects, and advantages of the present invention willbecome better understood when the following detailed description is readwith reference to the accompanying figures in which like charactersrepresent like parts throughout the figures, wherein:

FIG. 1 is a sub-sea BOP stack assembly, which may include one or morethermal control systems configured to control a temperature of anactuator coupled to a flow control device;

FIG. 2 is an embodiment of a subsea insulated structure having a thermalcontrol system configured to control a temperature of an actuatorcoupled to a flow control device;

FIG. 3 is a schematic of an embodiment of a thermal control systemconfigured to control a temperature of an actuator coupled to a flowcontrol device;

FIG. 4 is a schematic of an embodiment of a thermal control systemconfigured to control a temperature of an actuator coupled to a flowcontrol device;

FIG. 5 is a schematic of an embodiment of a thermal control systemconfigured to control a temperature of an actuator coupled to a flowcontrol device;

FIG. 6 is a schematic of an embodiment of a thermal control systemconfigured to control a temperature of an actuator coupled to a flowcontrol device; and

FIG. 7 is a schematic of an embodiment of a thermal control systemconfigured to control a temperature of an actuator coupled to a flowcontrol device.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. These described embodiments are only exemplary of thepresent invention. Additionally, in an effort to provide a concisedescription of these exemplary embodiments, all features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Moreover, the use of “top,” “bottom,” “above,” “below,” and variationsof these terms is made for convenience, but does not require anyparticular orientation of the components.

In the embodiments discussed in detail below, a thermal control systemis configured to control the temperature in subsea equipment. Forexample, the thermal control system may be disposed in subsea insulatedstructures having pipes or conduits running through the insulatedstructures. The pipes may route various system or operating fluids tofor from a well. For example, the fluids may include production oil fromthe well, and thus may be heated. The pipes may further include flowvalves, chokes, and so forth, within the insulated structures. Inaddition to the fluid pipes and other conduits, the insulated structuresare filled with sea water. As heated fluids (e.g., production oil) arerouted through the pipes, the sea water within the insulated structuresabsorbs heat transferred from the fluids flowing through the pipes.Additionally, the insulated structures retain the heat absorbed by thesea water, thereby substantially blocking release of the heat and energygenerated by the subsea system into the surrounding sea environment. Theheat retained in the insulated structures further operates tosubstantially reduce formation of hydrates in the choke and/or flowlines. The insulated structures may further include actuators configuredto operate the flow valves, chokes, and so forth. Additionally, theactuators may have electronic assemblies, processors, memory circuits,and mechanical components such as seals and gear oils that are heatsensitive. Without the disclosed thermal control system, due to the heattransferred to the actuators by the pipes and flow control devices andretained by the insulated structures, the actuators may reachtemperatures that cause the electronics assemblies and heat sensitivemechanical components to malfunction and fail. Accordingly, thedisclosed thermal control system is configured to maintain thetemperature in the insulated structure within a suitable temperaturerange to improve performance and prevent thermal damage of the actuator,flow control device, and other equipment in the insulated structure.

As discussed below, the disclosed thermal control system may have avariety of features to control the temperature in the subsea equipment.For example, the thermal control system may include a thermostat coupledto a heat exchanger. The heat exchanger may be coupled to an actuatorwhich is configured to regulate the operation of a flow control device.Specifically, the heat exchanger may be coupled to inlet and outletports of the insulated structure to enable a flow of exterior sea water(i.e., cold sea water outside the insulated structure) through the heatexchanger, thereby lowering the temperature of the actuator and theinterior sea water within the insulated structure surrounding theactuator. The thermostat is configured to control the flow of exteriorsea water through the heat exchanger based on temperature feedback, suchas a sensed temperature of the interior sea water or the actuator. Forexample, the thermostat may trigger a valve to open if the temperatureexceeds an upper threshold temperature, and the thermostat may triggerthe valve to close if the temperature drops below a lower thresholdtemperature. In certain embodiments, the valve may be disposed at theoutlet port.

Upon opening the valve, natural convection and buoyancy differencesbetween heated sea water within the heat exchanger and cold sea watersurrounding the insulated structure cause the heated sea water withinthe heat exchanger to escape the heat exchanger, thereby flowing to thelower temperature environment (i.e., the sea water surrounding theinsulated structure). Furthermore, as mentioned above, the insulatedstructure includes an inlet port coupled to the heat exchanger, allowingcold sea water surrounding the insulated structure to enter the heatexchanger. The cold sea water flowing into the heat exchanger absorbsheat from the actuator, thereby lowering the temperature of the actuatorand the sea water surrounding the actuator. Once the temperature of theactuator decreases to a certain level, the thermostat triggers the valveto close. With the valve closed, the actuator within the insulatedstructure begins to reheat from heat transferred by the fluids flowingthrough the pipes and flow control device within the insulatedstructure. Thus, the thermostat may trigger the valve to selectivelyopen and close to flow the exterior sea water through the heatexchanger, thereby maintaining the temperature of the actuator within asuitable temperature range.

The thermal control system may be used in various types of equipment.For instance, FIG. 1 depicts an exemplary resource extraction system 10that includes a well 12, what is colloquially referred to as a“christmas tree” 14 (hereinafter, a “tree”), and a receptacle 16. Theillustrated resource extraction system 10 can be configured to extracthydrocarbons (e.g., oil and/or natural gas). In some embodiments, theresource extraction system 10 may be disposed in a subsea environmentand/or configured to extract or inject other substances, such as thosediscussed above.

When assembled, the tree 14 couples to the well 12 and includes avariety of valves, fittings, and controls for operating the well 12. Forexample, the receptacle 16 may be in fluid communication with the well12 and may be configured to house a flow control device, such as a chokeor other valve. In the illustrated embodiment, the receptacle 16includes an insulated structure 18 (e.g., a choke body) having aninsulation cap 20 and an insert 22. In certain embodiments, the flowcontrol device within the receptacle 16 may be configured to regulatethe flow of a chemical through the tree 14 and into the well 12. Inother embodiments, the receptacle 16 and flow control device may bepositioned on a manifold of the resource extraction system 10. Asdiscussed in detail below, the flow control device may include a thermalcontrol system configured to control the temperature of an actuator ofthe flow control device.

FIG. 2 is a schematic of an embodiment of one of the insulatedstructures 18 of FIG. 1 having a thermal control system 48. Theillustrated embodiment shows pipes 50 passing through the insulatedstructure 18. Fluid flow through the pipes 50 is regulated by a flowcontrol device 52, which is operated by an actuator 54. As shown, theinsulated structure 18 includes the thermal control system 48 configuredto regulate a temperature of the actuator 54. In the illustratedembodiment, the insulated structure 18 has a body 56 and a lid 58.Additionally, the insulated structure 18 has a wall 57 with aninsulative layer 59. As discussed above, the insulated structure 18serves to retain heat and energy within the insulated structure 18. Forexample, at times when the BOP package 28 is shut down, the insulativestructure 18 may retain energy and/or heat within the insulativestructure 18 to reduce unnecessary energy and/or heat loss from the BOPpackage 28. Additionally, the heat retained by the insulated structure18 may reduce the formation of hydrates within the pipes 50 and the flowcontrol device 52.

The pipes 50 flow a fluid 60, such as a system or operating fluid, whichmay be heated. For example, the fluid 60 may be a production oil fromthe well. As mentioned above, the pipes 50 also include the flow controldevice 52. For example, the flow control device 52 may be a valve or achoke and may be configured to regulate a flow rate of the fluid 60through the pipes 50. The insulated structure 18 is also filled withinterior sea water 62, which surrounds the thermal control system 48,the pipes 50, the flow control device 52, and the actuator 54. Asdiscussed above, the interior sea water 62 absorbs heat from the fluid60 flowing through the pipes 50. Consequently, the interior sea water 62gradually increases in temperature while heated fluid 60 flows throughthe pipes 50. Similarly, the temperature of the interior sea water 62rises due to the insulated structure 18 retaining the heat transferredfrom the heated fluid 60 flowing through the pipes 50. For example,absent any temperature regulation in the insulated structure 18, theinterior sea water 62 may reach temperatures of approximately 120° F.,130° F., 140° F., 150° F., 160° F., 170° F., 180° F., 190° F., 200° F.,210° F., 220° F., 230° F., 240° F., 250° F., or more.

As shown, the interior sea water 62 within the insulated structure 18surrounds the actuator 54, which may include heat sensitive componentssuch as electronics, seals, and gear oil. As the temperature of theinterior sea water 62 increases, the actuator 54 and its components alsoincreases. Similarly, heat from the fluid 60 flowing through the pipes50 may be conducted through the flow control device 52 to the actuator54, as indicated by arrow 64. As the actuator 54 and its componentsabsorb heat from the interior sea water 62 and the flow control device52, the actuator 54 may reach temperatures that can cause heat sensitivecomponents of the actuator 54 to fail without the presently disclosedthermal control system 48. For example, without the present disclosedthermal control system 48, the actuator 54 and its components may beginto fail if the temperature of the actuator 54 is greater thanapproximately 100° F., 110° F., 120° F., 130° F., 140° F., or 150° F.

To regulate the temperature of the actuator 54, the insulated structure18 includes the thermal control system 48. In the illustratedembodiment, the thermal control system 48 includes a thermostat 65coupled to a heat exchanger 66 and a valve 67. The heat exchanger 66 iscoupled to the actuator 54 and/or the flow control device 52 to maintainthe temperature within a suitable range. In other embodiments, the heatexchanger 66 may be coupled to other components within the insulatedstructure 18. As described in detail below, the heat exchanger 66 mayinclude a variety of configurations, such as a coil, plate, or jacketheat exchanger 66. Once the actuator 54 reaches a predefined elevatedtemperature (e.g., an upper threshold temperature), the thermal controlsystem 48 operates to circulate exterior sea water 68 (i.e., sea wateroutside the insulated structure 18) through the heat exchanger 66,thereby transferring heat from the actuator 54 to the exterior sea water68. Specifically, the thermal control system 48 includes the thermostat65, which may include one or more temperature sensors, configured tomonitor the temperature of the actuator 54. Once the actuator 54 reachesthe predefined elevated temperature, the thermostat 65 of the thermalcontrol system 48 actuates the valve 67 to open an exit port 70,allowing heated water within the heat exchanger 66 to exit the heatexchanger 66. As mentioned above, natural convection and buoyancydifferences between heated sea water within the heat exchanger 66 andthe exterior sea water 68 surrounding the insulated structure 18 causethe heated sea water within the heat exchanger 66 to escape the heatexchanger 66 through an exit conduit 71 extending between an outlet 77of the heat exchanger 66 and the exit port 70, as indicated by arrow 72.

To replace the sea water that exits the heat exchanger 66 through theexit port 70, exterior sea water 68 (i.e., sea water from outside theinsulated structure 18) enters the heat exchanger 66 through an inletport 74. As indicated by arrow 76, the exterior sea water 68 flowsthrough an inlet conduit 78 extending between an inlet 80 of the heatexchanger 66 and the inlet port 74. More specifically, as sea waterexits the heat exchanger 66 through the exit port 70, a vacuum iscreated within the heat exchanger 66. This vacuum generates a flow ofexterior sea water 68 through the inlet port 74 and into the heatexchanger 66 (e.g., into a heat exchanger volume 82 of the heatexchanger 66). The exterior sea water 68 may have a temperature ofapproximately 35, 36, 37, 38, 39, or 40 degrees F. Therefore, as heatedsea water exits the heat exchanger 66 and is replaced by exterior seawater 68, the heat exchanger 66 will absorb heat from the actuator 54.In other words, the temperature difference between the actuator 54 andthe sea water within the heat exchanger 66 will cause heat from theactuator 54 to be transferred to the sea water within the heat exchanger66. As discussed below, once the temperature of the actuator 54 cools toa certain level (e.g., a lower threshold temperature), the thermostat 65of the thermal control system 48 operates to close the exit port 70 toblock the flow of sea water from the heat exchanger 66 through the exitport 70.

FIG. 3 is a schematic of the insulated structure 18 having the thermalcontrol system 48, illustrating the thermostat 65 coupled to the heatexchanger 66 and the valve 67. In the illustrated embodiment, the heatexchanger 66 comprises a coil 100. In certain embodiments, the coil 100may be coupled to the actuator 54, while, in other embodiments, the coil100 may be disposed about a perimeter of the actuator 54, but notphysically coupled to the actuator 54. Furthermore, the coil 100 may becoupled to, or disposed about, another component or portion of theinsulated structure 18. The coil 100 may be formed from metal tubingsuch as steel, copper, or the like. The thermal control system 48 thethermostat 65 and the valve 67 configured to regulate the flow throughthe heat exchanger 66, and thus the heat transfer away from the actuator54. Additionally, the thermal control system 48 includes filters 104disposed at the exit and inlet ports 70 and 74 of the thermal controlsystem 48. As will be appreciated, the filters 104 may block entry ofmarine growth, such as vegetation or animals, into the heat exchanger66. The illustrated embodiment includes similar elements and elementnumbers as the embodiment shown in FIG. 2.

As mentioned above, the thermostat 65 and the valve 67 are configured tocirculate exterior sea water 68 through the heat exchanger 66 once theactuator 54 reaches a predetermined elevated temperature. Specifically,the thermostat 65 is configured to open and close the valve 67 at theexit port 70 of the thermal control system 48. In the illustratedembodiment, the thermostat 65 includes a sensor 108 coupled to theactuator 54. The sensor 108 is configured to monitor the temperature ofthe actuator 54. For example, the sensor 108 may be a thermocouple,infrared sensor, or optical sensor. The thermostat 65 also includes acontroller 110 coupled to the sensor 108, and an actuator 112 coupled tothe controller 110. In certain embodiments, the controller 110 may be aprogrammable logic controller (PLC) or a distributed control system(DCS). When the actuator 54 reaches the predefined elevated temperature,the sensor 108 detects the predefined elevated temperature andcommunicates the event to the controller 110. Thereafter, the controller110 operates to engage the actuator 112, which is coupled to the valve67. Specifically, when the sensor 108 indicated that the actuator 54 hasreached the predefined elevated temperature (e.g., upper thresholdtemperature), the thermostat 65 (e.g., controller 110) triggers theactuator 112 to open the valve 67, thereby opening the exit port 70.

As mentioned above, with the exit port 70 opened, natural convection andbuoyancy differences between the heated sea water within the coil 100 ofthe heat exchanger 66 and the exterior sea water 68 surrounding theinsulated structure 18 cause the heated sea water within the coil 100 toescape the coil 100 through the exit port 70. As the heated sea waterfrom the coil 100 escapes through the exit port 70, exterior sea water68 from outside the insulated structure 18 enters the coil 100 of theheat exchanger 66 through the inlet port 74. In the manner discussedabove, heat will transfer from the actuator 54 to the exterior sea water68 that has entered the coil 100 through the inlet port 74, therebylowering the temperature of the actuator 54. As sea water continues toflow through the coil 100 and absorb heat from the actuator 54, theactuator 54 will eventually cool to a predefined lowered temperature(e.g., lower threshold temperature). For example, the predefined lowertemperature may be approximately 50 to 100, 60 to 90, or 70 to 80degrees F. Once the sensor 108 indicates that the temperature of theactuator 54 has reached the predefined lowered temperature, thecontroller 110 operates to engage the actuator 112 and close the valve67, thereby closing the exit port 70 and stopping the flow of sea waterthrough the coil 100. With the exit port 70 closed, the sea water withinthe coil 100 will being to increase in temperature as the actuator 54increases in temperature within the insulated structure 18. Eventually,the actuator 54 will reach the predefined elevated temperature again,and the thermal control system 48 will operate to cool the actuator 54again, in the manner described above. In the manner described above, thethermal control system 48 can maintain the temperature of the actuator54 within a suitable temperature range (e.g., between upper and lowerthreshold temperatures).

FIG. 4 is a schematic of the insulated structure 18 having the thermalcontrol system 48, illustrating a fin-type configuration of the heatexchanger 66. The illustrated embodiment includes similar elements andelement numbers as the embodiment shown in FIG. 3. In the illustratedembodiment, the heat exchanger 66 comprises a plurality of fins 130coupled to the actuator 54. For example, the fins 130 may be disposedabout a perimeter of the actuator 54 and extend radially outward fromthe actuator 54. In certain embodiments, the fins 130 may be constructedfrom a metal, such as copper, steel, aluminum, or other materialconfigured to conduct heat. Furthermore, while the illustratedembodiment shows four fins 130 coupled to the actuator 54, otherembodiments of the heat exchanger 66 may include other numbers of fins130. For example, the heat exchanger 66 may include approximately 1 to50, 2 to 40, 3 to 30, 4 to 20 or 5 to 10 fins 130. Additionally, theheat exchanger 66 includes a conduit 132 extending from the inlet port74 to the exit port 70. More specifically, the conduit 132 is coupled toand passes through the fins 130 secured to the actuator 54. As shown,the conduit 132 passes through each of the fins 130 multiple times. Inother words, the conduit 132 winds back and forth through the fins 130.The conduit 132 may be metal tubing formed from a metal such as copper,steel, or aluminum.

In the manner described above, the thermostat 65 (e.g., controller 110)opens the valve 67 to open the exit port 70 when the actuator 54 reachesthe predefined elevated temperature. The exterior sea water 68 entersthe conduit 132 through the inlet port 74 and passes through the heatexchanger 66. In this manner, the sea water within the conduit 132absorbs heat from the actuator 54. Specifically, as the temperature ofthe actuator 54 rises, heat from the actuator 54 is conducted to thefins 130. Subsequently, as sea water passes through the conduit 132coupled to the fins 130, the temperature difference between the seawater flowing through the conduit 132 and the fins 130 will cause thesea water to absorb heat from the fins 130. As heat from the fins 130 isabsorbed by the sea water flowing through the conduit 132, thetemperature of the fins 132, and thereby the actuator 54, is lowered. Asdescribed above, once the actuator 54 reaches a predefined loweredtemperature, the thermostat 65 (e.g., controller 110) closes the valve67 to close the exit port 70, thereby stopping the flow of exterior seawater 68 through the conduit 132 of the heat exchanger 66. In thismanner, the thermal control system 48 can maintain the temperature ofthe actuator 54 within a suitable temperature range (e.g., between upperand lower threshold temperatures).

FIG. 5 is a schematic of the insulated structure 18 having the thermalcontrol system 48, illustrating a jacket configuration of the heatexchanger 66 having a jacket configuration. The illustrated embodimentincludes similar elements and element numbers as the embodiment shown inFIG. 3. In the illustrated embodiment, the heat exchanger 66 comprises ajacket 150 coupled to the actuator 54. As shown, the jacket 150 of theheat exchanger 66 is coupled to and disposed about a perimeter 152 ofthe actuator 54. The jacket 150 forms an annular passage 154 about theperimeter 152 of the actuator 54. The jacket 150 may be coupled to andextends around the actuator 54 by fasteners or by a joining process,such as brazing or welding. Alternatively, the jacket 150 may beintegrally formed with the actuator 54. In other words, the jacket 150may be a permanently fixed component (e.g., an internal cavity of a caststructure) of the actuator 54. In one embodiment, the jacket 150 may beformed from a thermally conductive metal, such as copper, steel oraluminum. In the illustrated embodiment, the jacket 150 receives a seawater flow from an inlet conduit 156 connected to the inlet port 74.Similarly, the sea water flows from the jacket 150 to the exit port 70through an exit conduit 158.

In the manner described above, the thermostat 65 (e.g., controller 110)opens the valve 67 to open the exit port 70 when the actuator 54 reachesthe predefined elevated temperature. The exterior sea water 68 entersthe inlet conduit 156 through the inlet port 74 and flows into thejacket 150 of the heat exchanger 66. As the sea water flows through thejacket 150, the sea water absorbs heat from the actuator 54. Morespecifically, as sea water passes through the jacket 150 coupled to theactuator 54, the temperature difference between the sea water flowingthrough the jacket 150 and the actuator 54 will cause the sea water toabsorb heat from the actuator 54. As heat from the actuator 54 isabsorbed by the sea water flowing through the jacket 150, thetemperature of the actuator 54 is lowered. As described above, once theactuator 54 reaches a predefined lowered temperature, the thermostat 65(e.g., controller 110) closes the valve 67 to close the exit port 70,thereby stopping the flow of exterior sea water 68 through the jacket150 of the heat exchanger 66. In this manner, the thermal control system48 can maintain the temperature of the actuator 54 within a suitabletemperature range (e.g., between upper and lower thresholdtemperatures).

FIG. 6 is a schematic of the insulated structure 18 having the thermalcontrol system 48, illustrating a pump 170 of the system 48 configuredto force a flow of sea water 68 through the heat exchanger 66. Morespecifically, the pump 170 is disposed along an inlet conduit 172between the inlet port 74 and the heat exchanger 66. However, in otherembodiments, the pump 170 may be disposed along an exit conduit 174between the heat exchanger 66 and the exit port 70. The illustratedembodiment includes similar elements and element numbers as theembodiment shown in FIG. 3.

As shown, the operation of the pump 170 is regulated by the thermostat65 (e.g., controller 110). Additionally, a power source 176 providespower to the pump 170. In operation, when the actuator 54 reaches thepredefined elevated temperature, the thermostat 65 (e.g., controller110) operates the actuator 112 to open the valve 67. Simultaneously, inthe illustrated embodiment, the thermostat 65 (e.g., controller 110)operates the pump 170. In other words, the controller 170 turns the pump170 on after or while concurrently opening the valve 67. As will beappreciated, when the valve 67 is closed, i.e., when the temperature ofthe actuator 54 is below the predefined elevated temperature, the pump170 is not operating. When the pump 170 is turned on, the pump 170operates to force sea water through the inlet conduit 172 from the inletport 74 to the heat exchanger 66. In certain embodiments, the valve 67may be excluded from the thermal control system 48, and the pump 170 maybe placed in line with the exit conduit 174 to selectively enable anddisable the flow of sea water. Alternatively, the valve 67 and the pump170 may be integrated with one another. In the illustrated embodiment,the heat exchanger 66 may have any of a variety of configurations. Forexample, the heat exchanger 66 may have the fin 130 configuration, thecoil 100 configuration, or the jacket 150 configuration described above.

Furthermore, the pump 170 enables an elevated flow rate of exterior seawater 68 through the heat exchanger 66. Without the pump 170, the flowof sea water through the heat exchanger 66 is driven by convection andbuoyancy differences between the heated water within the heat exchanger66 and the cold exterior sea water 68 entering the heat exchanger 66through the inlet port 74, as described above. In the illustratedembodiment, the pump 170 provides an additional force to drive theexterior sea water 68 through the heat exchanger 66. In this manner, theflow rate of the exterior sea water 68 through the heat exchanger 66 isincreased and, consequently, the rate of heat transfer between theactuator 54 and the heat exchanger 66 may increase. Furthermore, thethermostat 65 (e.g., controller 110) may be configured to regulate thespeed of the pump 170 to vary the flow rate of the exterior sea water 68through the heat exchanger 66, and therefore vary the rate of heattransfer from the actuator 54. Once the actuator 54 reaches a predefinedlowered temperature, the thermostat 65 (e.g., controller 110) mayselectively close the valve 67 to close the exit port 70 and turn offthe pump 170, thereby stopping the flow of exterior sea water 68 throughthe heat exchanger 66. In this manner, the thermal control system 48 canmaintain the temperature of the actuator 54 within a suitabletemperature range (e.g., between upper and lower thresholdtemperatures).

FIG. 7 is a schematic of the insulated structure 18 having the thermalcontrol system 48, illustrating an embodiment of the thermostat 65.Specifically, in the illustrated embodiment, the thermostat 65 includesa thermocouple 200 and a thermally actuated valve 202 having a thermalactuator 204 and a valve mechanism 206. The thermocouple 200 is coupledto the actuator 54 and is configured to measure the temperature of theactuator 54. When the actuator 54 reaches the predefined elevatedtemperature, the thermocouple 200 communicates the event to thethermally actuated valve 202. In response to the actuator 54 reachingthe predefined elevated temperature, the thermal actuator 204 triggersthe valve mechanism 206 of the thermally actuated valve 202. The valvemechanism 206 opens the exit port 70, allowing the sea water within theheat exchanger 66 to flow out of the heat exchanger 66 and allowingexterior sea water 68 to enter the heat exchanger 66 to absorb heat fromthe actuator 54, in the manner described above. Thereafter, when theactuator 54 has reached the predefined lowered temperature, thethermocouple 200 communicates the event to the thermally actuated valve202, causing the valve mechanism 206 to close the exit port 70 and stopthe flow of sea water through the heat exchanger 66. In this manner, thethermal control system 48 can maintain the temperature of the actuator54 within a suitable temperature range (e.g., between upper and lowerthreshold temperatures).

As discussed above, embodiments of the thermal control system 48 monitorand control the temperature within the insulated structure 18, andparticularly the temperature of the actuator 54. Moreover, the thermalcontrol system 48 is configured to maintain the temperature of theactuator 54 within a predefined temperature range (e.g., between thepredefined elevated temperature and the predefined lowered temperature).The regulation of the temperature of the actuator 54 helps prevent theactuator 54 from being exposed to elevated temperatures, which may causethe actuator 54 and its subcomponents to malfunction or fail.Additionally, while the embodiments of the thermal control system 48discussed above are configured to maintain the temperature of theactuator 54 within a predefined temperature range, other embodiments ofthe thermal control system 48 may be configured to maintain thetemperature of any component within the insulated structure 18.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A system, comprising: an underwater assembly, comprising: a flowcontrol device: and an actuator coupled to the flow control device,wherein the actuator is configured to actuate the flow control device;an insulated housing surrounding the flow control device and theactuator, wherein the insulated housing is configured to retain heat;and a thermal control system comprising a heat exchanger configured tocontrol a temperature of the actuator.
 2. The system of claim 1, whereinthe heat exchanger comprises a heat exchanger volume isolated from aninterior of the insulated housing, and the thermal control system isconfigured to circulate a fluid through the heat exchanger volume. 3.The system of claim 2, wherein the thermal control system comprises aninlet passage extending from an exterior through a wall of the insulatedhousing, through the interior of the insulated housing, and to an inletof the heat exchanger.
 4. The system of claim 3, wherein the thermalcontrol system comprises an outlet passage extending from an outlet ofthe heat exchanger, through the interior of the insulated housing, andthrough the wall to the exterior of the insulated housing.
 5. The systemof claim 4, comprising a valve coupled to the outlet passage, whereinthe thermal control system is configured to open or close the valve inresponse to at least one temperature threshold.
 6. The system of claim5, wherein the valve comprises a thermally actuated valve unit having athermal actuator coupled to a valve mechanism, and the thermal actuatoris configured to open or close the valve mechanism in response to the atleast one temperature threshold.
 7. The system of claim 5, wherein thethermal control system comprises an actuation system configured to openor close the valve in response to the at least one temperaturethreshold, wherein the actuation system comprises a temperature sensor,a controller, and an actuator.
 8. The system of claim 2, wherein theheat exchanger comprises a coil disposed about the actuator, and thecoil is configured to circulate the fluid.
 9. The system of claim 2,wherein the heat exchanger comprises a plurality of fins coupled to theactuator and a conduit coupled to the plurality of fins, and the conduitis configured to circulate the fluid.
 10. The system of claim 2, whereinthe heat exchanger comprises a jacket disposed about and coupled to theactuator, and the jacket defines a volume configured to circulate thefluid.
 11. The system of claim 2, wherein the thermal control systemcomprises a pump configured to force circulation of the fluid throughthe heat exchanger volume.
 12. The system of claim 2, wherein the fluidcomprises sea water that enters the heat exchanger volume from anexterior of the insulated housing.
 13. A system, comprising: anunderwater thermal control system, comprising: a heat exchangerconfigured to control a temperature of an actuator disposed in aninsulated housing; an inlet passage configured to pass a water flow froman exterior of the insulated housing into the heat exchanger; an outletpassage couple configured to pass the water flow from the heat exchangerto the exterior of the insulated housing; and a valve coupled to theoutlet passage, wherein the valve is configured to open and close tocontrol circulation of the water flow through the inlet passage, theheat exchanger, and the outlet passage based on temperature feedback.14. The system of claim 13, comprising a thermostat configured tooperate the valve based on a comparison of the temperature feedback toat least one temperature threshold.
 15. The system of claim 14, whereinthe thermostat comprises a temperature sensor, a controller, and a valveactuator coupled to the valve
 16. The system of claim 15, wherein thethermostat is configured to operate a pump to force the water flowthrough the heat exchanger.
 17. The system of claim 13, comprising amineral extraction component having the actuator.
 18. A method,comprising: sensing a temperature at or above an upper thresholdtemperature within an insulated underwater housing that contains anactuator coupled to a flow control device; initiating a flow of waterfrom a surrounding water through a heat exchanger within the insulatedunderwater housing if the temperature is at or above the upper thresholdtemperature; sensing the temperature at or below a lower thresholdtemperature within the insulated underwater housing; and terminating theflow of water through the heat exchanger if the temperature is at orbelow the lower threshold temperature.
 19. The method of claim 18,comprising maintaining the temperature of an underwater mineralextraction component within a temperature range, wherein the underwatermineral extraction component comprises the insulated underwater housing,the actuator, and the flow control device.
 20. The method of claim 19,wherein initiating the flow of water comprises opening a valve to enablethe flow by natural buoyancy and temperature differences between theheat exchanger and the water surrounding the insulated underwaterhousing.